J wrote:
> Hello,
>
> Has anyone made a circuit that has something like some digital logic
> amd a pic with some long conductor paths that will drive a fluorescent
> bulb? Currently I am isolating the AC signal by having an analog
> ground plane that is isolated from the digital ground plane. There is
> a common ground area in which both planes are connected by a path that
> is at least .50 inches wide. Has anyone done something similiar and
> how much noise did the bulb create? Any ideas on how to keep the
> noise from traveling from the AC ground plane to the Digital ground
> plane via the common ground area? Should I keep the pathway to the
> common ground area to a certain minimum? Any help is appreciated!
> THANKS!
Your biggest challenge is predicting where the ground currents flow, and
then try to layout the grounds to minimize voltage differences between
the analog and digital ground pins at the uC, and simultaneously
minimize voltage differentials across the analog grounding that lay
between the ground of the analog signal source and uC analog ground
pins. From memory when I build my AVR controlled 12VDC powered 18W
fluorescent switch mode driver circuit, I managed about 5 LSB noise
(before software filtering) out of the built in 10bit ADC. Its wasn't
easy (at least for me), and took me three or so PCB designs.
Adam